WO2007134620A1

WO2007134620A1 - Method for preparing a component consisting of an electroconductive base material in order to carry out an erosive process

Info

Publication number: WO2007134620A1
Application number: PCT/EP2006/004786
Authority: WO
Inventors: Viktor Georgiev; Francis-Jurjen Ladru; Gerhard Reich
Original assignee: Siemens Aktiengesellschaft
Priority date: 2006-05-19
Filing date: 2006-05-19
Publication date: 2007-11-29
Also published as: WO2007134916A1

Abstract

The invention relates to a method for preparing a component (1) consisting of an electroconductive base material in order to carry out an erosive process. During said method, an electrically insulating coating (39) is sprayed onto the surface (27) of the base material. The areas (35) in which the erosive process is to be carried out are kept free of coating material during the spraying of the coating.

Description

A method of preparing a component of an electrically conductive base material to perform a

erosion process

The present invention relates to a method of preparing a component of electrically conductive base material to perform an erosion process.

Highly thermally stressed components are often provided with a heat-insulating coating to keep the heat load of the components low. In addition, cooling air holes are often introduced into such components to allow the generation of a cooling air film over the component. The cooling air film leads to a further cooling and thus to a further reduction of the thermal load. In particular, gas turbine blades, ie running or guide vanes of gas turbines, have such cooling air holes and thermal barrier coatings.

A common method for producing the cooling air holes in the metallically conductive base material of the turbine blades is the erosion with the aid of erosion electrodes. Since this method requires a current flow between the electrically conductive base material and the erosion electrodes, the introduction of the cooling air holes takes place before the application of the electrically insulating thermal barrier coating.

Because the existing cooling air holes are closed when applying the thermal barrier coating, they must be opened again after applying the thermal barrier coating. The opening can be done, for example, by means of a high-pressure fluid, which is blown from the inside of the turbine blades through the cooling air holes. Such a method is, for example, in JP

9158702 described. It is important to ensure that no damage to the coating in the vicinity of the holes occurs when blowing through the cooling air holes. Another way to reopen the cooling air holes after applying the thermal barrier coating is to plug them with a plug before applying the thermal barrier coating. After the thermal barrier coating has been applied, the plug is removed again. In JP 4236757 a method is described in which a plug is used, which is burned out after the application of the thermal barrier coating. Again, make sure that the removal of the plug does not damage the thermal barrier coating.

One way to make the opening of the cooling air holes only after the application of the thermal barrier coating is described in JP 9136260. After applying a thermal barrier coating on the base material of a turbine blade, the thermal barrier coating is removed there, where the cooling air holes are to be introduced, by means of a blasting process again. Subsequently, the cooling air holes are introduced by means of erosion electrodes at the exposed locations in the base material. However, care must be taken when removing the thermal barrier coating by means of the blasting process that the blasting does not result in damage to the ceramic thermal insulation layer outside the areas intended for the introduction of the cooling air holes.

The object of the present invention is to provide an advantageous method for preparing a component made of an electrically conductive base material for performing an erosion process.

A further object is to provide an advantageous method for producing a component from an electrically conductive base material with an electrically insulating coating and recesses introduced into the base material. These objects are achieved by a method for preparing a component according to claim 1 and by A method for producing a component according to claim 7 solved. The dependent claims contain advantageous embodiments of the method.

In the method according to the invention for preparing a component of an electrically conductive base material for performing an erosion process, an electrically insulating coating is sprayed onto the surface of the base material. Those areas of the component surface in which the erosion process is to be carried out are kept free during the spraying of the coating of coating material.

Because the surface of the base material is kept from the outset by the coating material where the erosion process is to be carried out for forming recesses, such as cooling air openings, it is no longer necessary to remove excess coating material after application of the coating. The risk of damaging the already applied coating by removing coating material is thereby eliminated. In addition, it is possible to reduce the number of work steps involved in the erosive introduction of recesses, since the removal of the coating is eliminated, which can have a cost-effective effect on the manufacture of the components.

The keeping clear of those areas in which the erosion process is to be carried out is possible in particular by generating a spray shadow. Since this is possible without contact, this procedure is particularly gentle for the surface to be coated. For generating the injection shadow, in particular a template can be arranged above the component surface during spraying. This template can also be designed in three dimensions. It then has, for example, an inverse structure to be erosively formed, which is arranged relative to the component surface and to the injection direction such that the resulting spray shadow the opening area of the recess in the surface corresponds.

The inventive method is particularly suitable for the manufacture of turbine blades, so as runners or vanes of gas turbines to which a thermal barrier coating is applied as an electrically insulating coating and in the means of the erosion cooling air holes are to be introduced as recesses. Since the integrity of the thermal barrier coating is particularly important in the case of gas turbine blades, the method according to the invention makes a valuable contribution to improving the production of gas turbine blades with cooling-air bores. As inverse structures of a three-dimensional template for generating the spray shadow at the locations where the cooling air holes are to be introduced, for example, pins can be used.

Suitable spraying methods for applying the electrically insulating coating are, in particular, thermal spraying methods. But also non-thermal spray methods, such as. Cold gas spraying, can be used in principle.

The method of preparing a component of an electrically conductive base material for performing an erosion process may be adapted to a manufacturing method for manufacturing a component of an electrically insulating base material having an electrically insulating coating applied to the surface of the base material and at least one eroding by the base material be extended to the application of the electrically insulating coating introduced into the base material recess when after preparing the component according to the preparation method according to the invention at least one

Recess is introduced by means of an erosion process where the component surface has been kept free of the coating material. Further features, properties and advantages of the present invention will become apparent from the following description of an embodiment with reference to the accompanying figures.

1 schematically shows a section of a rotor blade of a gas turbine.

2 shows a template for producing a spray shadow during the injection of a thermal insulation coating on the turbine blade in a plan view of the leading edge of the turbine blade.

Fig. 3 shows the turbine blade of Fig. 2 in one

Section perpendicular to the leading edge of the turbine blade.

Fig. 4 shows a detail of Fig. 3 in an enlarged view.

FIG. 5 shows the turbine blade of FIG. 3 during the FIG

EDM process for introducing cooling air bores.

6 shows a perspective view of a rotor blade or guide vane of a turbomachine.

FIG. 6 shows a perspective view of a moving blade 120 or guide blade 130 of a turbomachine that extends along a longitudinal axis 121.

The turbomachine may be a gas turbine of an aircraft or a power plant for power generation, a steam turbine or a compressor. The blade 120, 130 has along the longitudinal axis 121 consecutively a fastening region 400, a blade platform 403 adjacent thereto and an airfoil 406 and a blade tip 415. As a guide blade 130, the blade 130 may have at its blade tip 415 another platform (not shown).

In the mounting region 400, a blade root 183 is formed, which serves for attachment of the blades 120, 130 to a shaft or a disc (not shown). The blade root 183 is designed, for example, as a hammer head. Other designs as Christmas tree or Schwalbenschwanzfuß are possible. The blade 120, 130 has a leading edge 409 and a trailing edge 412 for a medium flowing past the airfoil 406.

In conventional blades 120, 130, for example, solid metallic materials, in particular superalloys, are used in all regions 400, 403, 406 of the blade 120, 130. Such superalloys are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949; These writings are with respect. the chemical composition of the alloy part of the disclosure. The blade 120, 130 can hereby by a casting process, also by means of directed solidification, by a

Forging process, be made by a milling process or combinations thereof.

Workpieces with a monocrystalline structure or structures are used as components for machines which are exposed to high mechanical, thermal and / or chemical stresses during operation. The production of such monocrystalline workpieces, for example, by directed solidification from the melt. These are casting methods in which the liquid metallic alloy solidifies into a monocrystalline structure, ie a single-crystal workpiece, or directionally. In doing so, dendritic crystals are aligned along the heat flow and form either a stalk-critical stalline grain structure (columnar, ie grains which extend over the entire length of the workpiece and here, in general parlance, are referred to as directionally solidified) or a monocrystalline structure, ie the entire workpiece consists of a single crystal. In these processes, it is necessary to avoid the transition to globulitic (polycrystalline) solidification, since non-directional growth necessarily produces transverse and longitudinal grain boundaries which negate the good properties of the directionally solidified or monocrystalline component. The term "directionally solidified structures" generally refers to single crystals that have no grain boundaries or at most small angle grain boundaries, as well as stem crystal structures that have grain boundaries running in the longitudinal direction but no transverse grain boundaries. These second-mentioned crystalline structures are also known as directionally solidified structures. Such methods are known from US Pat. No. 6,024,792 and EP 0 892 090 A1; These writings are with respect. the solidification process part of the disclosure.

Likewise, the blades 120, 130 may have coatings against corrosion or oxidation, e.g. B. (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co),

Nickel (Ni), X is an active element and stands for yttrium (Y) and / or silicon and / or at least one element of the rare earths, or hafnium (Hf)). Such alloys are known from EP 0 486 489 B1, EP 0 786 017 B1, EP 0 412 397 B1 or EP 1 306 454 A1, which should be part of this disclosure with regard to the chemical composition of the alloy. The density is preferably 95% of the theoretical density. A protective aluminum oxide layer (TGO = thermal grown oxide layer) is formed on the MCrAlX layer (as an intermediate layer or as the outermost layer).

On the MCrAlX may still be present a thermal barrier coating, which is preferably the outermost layer, and exists for example ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , ie it is not, partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide. The thermal barrier coating covers the entire MCrAlX layer. Suitable coating processes, such as electron beam evaporation (EB-PVD), produce stalk-shaped grains in the thermal barrier coating. Other coating methods are conceivable, for example atmospheric plasma spraying (APS), LPPS, VPS or CVD. The thermal barrier coating may have porous, micro- or macro-cracked grains for better thermal shock resistance. The thermal barrier coating is therefore preferably more porous than the MCrAlX layer.

Refurbishment means that components 120, 130 may need to be deprotected after use (e.g., by sandblasting). This is followed by removal of the corrosion and / or oxidation layers or products. Optionally, even cracks in the component 120, 130 are repaired. This is followed by a re-coating of the component 120, 130 and a renewed use of the component 120, 130.

The blade 120, 130 may be hollow or solid. If the blade 120, 130 is to be cooled, it is hollow and may still film cooling holes 418 (indicated by dashed lines) on.

1 shows a schematic representation of a section of a rotor blade of a gas turbine. The rotor blade 1 consists of a metallic base material and has a leading edge 3 and a trailing edge 5, between which a pressure side 7 and a suction side 9 extend. In the pressure side 7 and in the suction side 9 cooling air holes 11, 13, 15 are arranged, is blown through during the operation of the gas turbine cooling air, which lays as a cooling air film around the turbine blade 1. The turbine blade 1 is provided for thermal insulation against the hot exhaust gases flowing around it during operation of the gas turbine plant with a WärmedämmbeSchichtung. The thermal barrier coating is applied by means of a spraying process. In the present embodiment, atmospheric plasma spraying is used, which is a special thermal spraying process.

According to the invention, the ceramic thermal barrier coating is first applied during the manufacture of the turbine blade illustrated in FIG. 1, before the cooling air bores 11, 13, 15 are introduced into the metallic base material of the turbine blade 1 by means of EDM drilling. Since EDM drilling requires a counter electrode to the erosion electrode, the ceramic thermal barrier coating can not be drilled with this method.

In order to prevent the application of ceramic thermal barrier coating on those surface areas, which later form the outlet openings of the cooling air holes 11, 13, 15, a stencil 17 is placed over the surface 27 of the turbine blade 1 during the spraying of the coating, as shown in FIGS Figures 2 to 4 is shown. The template 17 is equipped with a number of pins 19 fixed to a carrier 21. The carrier passes into a holder 23, to which the template 17 is held during spraying. The template 17 is stopped before the start of spraying to the surface of the uncoated turbine blade 1 that the tips 25 of the pins are located at a very small distance above the surface 27 of the turbine blade 1 (see Fig.4).

The spattering of the ceramic material takes place with the aid of a spray nozzle 29, from which the ceramic material is sprayed in an injection direction 33. The ceramic material leaving the spray nozzle 29 forms a spray cone 31, which represents a largely symmetrical distribution of material around the spray direction 33 of the spray nozzle 29. Due to the large The spatial proximity of the pins 19 to the surface 27 of the turbine blade forms a spray shadow 37 between the tips 25 of the pins 19 and certain areas 35 of the surface 27. In the spray-shadowed area 35 of the surface 27, the syringe ceramic material can

Not reach surface 27. This area is therefore not coated during the spraying process.

After the ceramic thermal barrier coating 39 has been applied to the surface 27 of the turbine blade 1, the areas 35 located in the spray shadow remain uncovered. In addition, during coating, the pins 19 and the injection direction 33 are oriented relative to one another such that the uncoated regions 35 correspond in shape exactly to the shape of the exit surfaces of the cooling air bores 11, 13, 15 to be formed in the component surface.

After the turbine blade 1 has been prepared for the erosion process, the erosion electrodes 41 are brought to the uncoated regions 35 and the erosion drilling started. In the course of the erosion process, the erosion electrodes 41 (see FIG. 5) are continuously tracked into the base material 43 until it has been broken through and a central cavity 45 of the turbine blade 1 has been reached. After reaching the central cavity 45, the corresponding cooling air hole is completed.

With the method according to the invention, cooling air bores can be introduced into the turbine blades after the application of a ceramic thermal barrier coating. The removal of ceramic thermal barrier coating at the locations where the cooling air holes are to be introduced, is not necessary. The ceramic thermal barrier coating 39 therefore remains unchanged after application, so that the risk of damaging the thermal barrier coating by local removal does not exist. The method according to the invention has been described using the example of the preparation of turbine blades for the introduction of cooling air bores by EDM drilling. However, it can also be used for introducing other recesses, for example grooves. These can then be introduced by means of a sinking process as the erosion process in the component surface.

Also, the component does not need to be a turbine blade. The invention can basically be used for preparing and producing such components which consist of an electrically conductive base material and which, after completion, should have an electrically insulating surface coating and recesses in the base material. As recesses are blind or through holes, grooves, etc. into consideration.

Claims

claims

A method of preparing a component (1) of an electrically conductive base material for performing an erosion process, wherein an electrically insulating coating (39) is sprayed onto the surface (27) of the base material,

characterized in that

those areas (35) in which the erosion process is to be carried out are kept free when spraying the coating onto the coating material.

2. The method according to claim 1, characterized in that

keeping clear by generating a spray shadow (37).

3. The method according to claim 2, characterized in that

for generating the spray shadow (37), a template (17) is arranged above the component surface (27).

4. The method according to claim 3, characterized in that

the template (17) has an inverse structure (19) relative to the recesses, which is arranged relative to the component surface (27) and the injection direction (33) such that the resulting spray shadow (37) of the opening surface of the recess in the surface (27 ) corresponds.

5. The method according to any one of the preceding claims, characterized in that

the component is a turbine blade (1) to which a thermal barrier coating is applied as an electrically insulating surface coating and that for producing the spray shadow (37) pins (19) are used as an inverse structure for cooling air holes.

6. The method according to any one of the preceding claims, characterized in that

the spraying process is a thermal spraying process.

7. A method for producing a component (1) from an electrically conductive base material with an electrically insulating coating (39) applied to the surface (27) of the base material and at least one into the base material by an erosion process after application of the electrically insulating coating ( 39) introduced recess, characterized in that

the component (1) is subjected to the method according to one of claims 1 to 6 before the recesses are introduced by means of an erosion process where the component

Surface has been kept free of the coating material.